This invention relates generally to shoes, and more particularly to shoes wherein light weight and the ability to tailor the stiffness and flexure of the shoe is an important consideration.
Shoes encounter tremendous forces during running or sports. Over the years, efforts have been made to reduce the resultant stresses on the feet and legs. One advance in this area has been the incorporation of cushioning material in the shoe sole to cushion the foot as the shoe strikes the ground. This cushioning material is typically formed into a layer called the xe2x80x9cmidsolexe2x80x9d which is interposed between the ground-engaging xe2x80x9coutsolexe2x80x9d and the shoe upper. The cushioning midsole, which should also flex with the foot, is typically made of ethyl-vinyl-acetate (EVA) or polyurethane (PU), although other resilient, cushioning materials could be used.
While the cushioning provided by a midsole is an advantage, its added weight hinders the performance of athletic shoes (particularly running shoes), which must be as light as possible. The problem of added weight from the midsole is recognized in U.S. Pat. No. 5,319,866 issued to Foley et al. Foley et al. attempts to solve the problem by substituting an arch support in place of the midsole and outsole underlying the arch area of the foot.
The use of a midsole between the outsole and the upper also positions the foot higher above the ground, creating a less stable platform for the foot. This problem is addressed to some degree in U.S. Pat. No. 4,542,598 issued to Misevich et al. Misevich teaches use of a heel plate between two heel midsole layers to support and cushion the heel, and a forefoot board inside the upper over a forefoot midsole layer to support and cushion the forefoot. As in Foley, Misevich eliminates the midsole beneath the arch, thereby saving some weight. Unlike Foley, however, Misevich does not provide any additional structure to support the arch.
The negative effects of the impact to the feet and legs can be amplified if the shoes are not properly shaped and tuned to the particular sport, and to the individual""s foot. Mass-produced athletic shoes come in standard sizes and shapes, and usually include an arch support designed to fit a xe2x80x9cstandardxe2x80x9d foot. Prior art shoes, such as those typified by Foley and Misevich, include no provision for tailoring the shoe to fit an individual foot, except for the use of orthotics. Orthotics are well-known in the art, and are exemplified by U.S. Pat. No. 4,803,747 issued to Brown. Orthotics, however useful, represent additional, undesirable weight, and also stiffen the shoe and otherwise compromise its performance.
Accordingly, a need remains for a light-weight shoe that minimizes the material in the sole, adequately supports the foot, and which can be readily customized for an individual""s foot or for a particular activity.
It is, therefore, an object of the invention to provide a shoe, in particular an athletic shoe, which can be customized to support the foot in accordance with requirements of a particular sport or activity.
It is another object of the invention to eliminate the need for an outsole and midsole which span substantially the entire length of the shoe.
A shoe according to the invention includes an upper, a chassis, or support member, attached to the underside of the upper to support the foot, and one or more ground-engaging sole elements affixed to the bottom of the chassis at discrete locations. Portions of the chassis are left exposed and unsupported by the sole elements. The weight of the shoe is thereby minimized because the full-length midsole and outsole have been replaced by the discrete sole elements.
The structural chassis may be contoured to conform to the underside of the foot. In one embodiment, the structural chassis has one or more notches or slots in locations selected to permit a desired flexure of the foot. The length and width of the notches can be varied to vary the shoe""s flexibility. Alternatively, the structural chassis can be without flexure notches, and rely instead on differing thicknesses of materials to vary its flexibility in different areas of the shoe.
A shoe according to the present invention utilizes a single structure for altering the support and flex of the shoe, thereby overcoming the disadvantage in the prior art that requires multiple elements to be modified to achieve the same result.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings.